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Fix #459 - properly support remote SPI with pigpio
Sorry! Dave's messing around with the pin implementations again. Hopefully the last time. The pin_factory is now really a factory object which can be asked to produce individual pins or pin-based interfaces like SPI (which can be supported properly via pigpio).
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Dave Jones
@@ -11,68 +11,68 @@ are concerned with. However, some users may wish to take advantage of the
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capabilities of alternative GPIO implementations or (in future) use GPIO
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extender chips. This is the purpose of the pins portion of the library.
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When you construct a device, you pass in a GPIO pin number. However, what the
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library actually expects is a :class:`Pin` implementation. If it finds a simple
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integer number instead, it uses one of the following classes to provide the
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:class:`Pin` implementation (classes are listed in favoured order):
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When you construct a device, you pass in a pin specification. However, what the
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library actually expects is a :class:`Pin` implementation. If it finds anything
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else, it uses the existing ``Device._pin_factory`` to construct a :class:`Pin`
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implementation based on the specification.
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1. :class:`gpiozero.pins.rpigpio.RPiGPIOPin`
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Changing the pin factory
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========================
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2. :class:`gpiozero.pins.rpio.RPIOPin`
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The default pin factory can be replaced by specifying a value for the
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``GPIOZERO_PIN_FACTORY`` environment variable. For example:
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3. :class:`gpiozero.pins.pigpiod.PiGPIOPin`
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.. code-block:: console
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4. :class:`gpiozero.pins.native.NativePin`
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pi@raspberrypi $ GPIOZERO_PIN_FACTORY=native python
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Python 3.4.2 (default, Oct 19 2014, 13:31:11)
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[GCC 4.9.1] on linux
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import gpiozero
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>>> gpiozero.Device._pin_factory
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<gpiozero.pins.native.NativeFactory object at 0x762c26b0>
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You can change the default pin implementation by over-writing the
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``pin_factory`` global in the ``devices`` module like so::
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The following values, and the corresponding :class:`Factory` and :class:`Pin`
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classes are listed in the table below. Factories are listed in the order that
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they are tried by default.
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from gpiozero.pins.native import NativePin
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import gpiozero.devices
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# Force the default pin implementation to be NativePin
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gpiozero.devices.pin_factory = NativePin
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+---------+-----------------------------------------------+-------------------------------------------+
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| Name | Factory class | Pin class |
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+=========+===============================================+===========================================+
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| rpigpio | :class:`gpiozero.pins.rpigpio.RPiGPIOFactory` | :class:`gpiozero.pins.rpigpio.RPiGPIOPin` |
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+---------+-----------------------------------------------+-------------------------------------------+
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| rpio | :class:`gpiozero.pins.rpio.RPIOFactory` | :class:`gpiozero.pins.rpio.RPIOPin` |
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+---------+-----------------------------------------------+-------------------------------------------+
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| pigpio | :class:`gpiozero.pins.pigpiod.PiGPIOFactory` | :class:`gpiozero.pins.pigpiod.PiGPIOPin` |
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+---------+-----------------------------------------------+-------------------------------------------+
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| native | :class:`gpiozero.pins.native.NativeFactory` | :class:`gpiozero.pins.native.NativePin` |
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+---------+-----------------------------------------------+-------------------------------------------+
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If you need to change the default pin factory from within a script, use the
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``Device._set_pin_factory`` class method, passing in the instance of the new
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factory to use. This is only supported at script startup (replacing the factory
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closes all existing pin instances which can have interesting consequences for
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any devices using them)::
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from gpiozero.pins.native import NativeFactory
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from gpiozero import *
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Device._set_pin_factory(NativeFactory())
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from gpiozero import LED
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# This will now use NativePin instead of RPiGPIOPin
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led = LED(16)
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``pin_factory`` is a concrete descendent of the abstract :class:`Pin` class.
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The descendent may take additional parameters in its constructor provided they
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are optional; GPIO Zero will expect to be able to construct instances with
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nothing more than an integer pin number.
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However, the descendent may take default information from additional sources.
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Certain factories may take default information from additional sources.
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For example, to default to creating pins with
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:class:`gpiozero.pins.pigpiod.PiGPIOPin` on a remote pi called ``remote-pi``
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you can set the :envvar:`PIGPIO_ADDR` environment variable when running your
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script::
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script:
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$ PIGPIO_ADDR=remote-pi python my_script.py
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.. code-block:: console
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It is worth noting that instead of passing an integer to device constructors,
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you can pass an object derived from :class:`Pin` itself::
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from gpiozero.pins.native import NativePin
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from gpiozero import LED
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led = LED(NativePin(16))
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In future, this separation of pins and devices should also permit the library
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to utilize pins that are part of IO extender chips. For example::
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from gpiozero import IOExtender, LED
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ext = IOExtender()
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led = LED(ext.pins[0])
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led.on()
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.. warning::
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While the devices API is now considered stable and won't change in
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backwards incompatible ways, the pins API is *not* yet considered stable.
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It is potentially subject to change in future versions. We welcome any
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comments from testers!
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$ export GPIOZERO_PIN_FACTORY=pigpio
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$ PIGPIO_ADDR=remote-pi python3 my_script.py
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.. warning::
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@@ -83,41 +83,48 @@ to utilize pins that are part of IO extender chips. For example::
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actual raspberry pie, you have only yourself to blame.
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RPiGPIOPin
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==========
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RPi.GPIO
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========
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.. autoclass:: gpiozero.pins.rpigpio.RPiGPIOFactory
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.. autoclass:: gpiozero.pins.rpigpio.RPiGPIOPin
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RPIOPin
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=======
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RPIO
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====
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.. autoclass:: gpiozero.pins.rpio.RPIOFactory
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.. autoclass:: gpiozero.pins.rpio.RPIOPin
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PiGPIOPin
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=========
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PiGPIO
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======
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.. autoclass:: gpiozero.pins.pigpiod.PiGPIOFactory
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.. autoclass:: gpiozero.pins.pigpiod.PiGPIOPin
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NativePin
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=========
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Native
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======
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.. autoclass:: gpiozero.pins.native.NativeFactory
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.. autoclass:: gpiozero.pins.native.NativePin
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Abstract Pin
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Base classes
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============
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.. autoclass:: Factory
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:members:
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.. autoclass:: Pin
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:members:
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Local Pin
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=========
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.. autoclass:: LocalPin
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.. autoclass:: SPI
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:members:
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